Method for filling an evacuated electron tube with gas to atmospheric pressure

ABSTRACT

Method includes scribing a circumferential cut on the glass exhaust tubulation of an electron tube, positioning the tubulation inside a close-fitting, closed chamber, cracking the tubulation on the cut, and slowly filling the chamber and tube with gas at a low rate of inflow to atmospheric pressure. Apparatus includes a close-fitting, closed chamber having a flexible portion that seals over the tubulation, a solid portion that closely fits over the tubulation, and a means to fill the tube and chamber with gas at a low rate of inflow to atmospheric pressure.

United States Patent Thall [54] METHOD FOR FILLING AN EVACUATED ELECTRONTUBE WITH GAS TO ATMOSPHERIC PRESSURE [72] Inventor: Earle SolomonThall, Waverly, Pa.

[451 July 25,1972

3,316,685 5/1967 Hansel ..29/413 X 3,390,033 6/1968 Brown ...29/427 X3,404,933 10/1968 Weideman ..316/2 Primary ExaminerJohn F. CampbellAssistant ExaminerRichard Bernard Lazarus Attorney-Glenn l-l. BruestleABSTRACT Method includes scribing a circumferential cut on the glassexhaust tubulation of an electron tube, positioning the tubulationinside a close-fitting, closed chamber, cracking the tubulation on thecut, and slowly filling the chamber and tube with gas at a low rate ofinflow to atmospheric pressure. Apparatus includes a close-fitting,closed chamber having a flexible portion that seals over the tubulation,a solid portion that closely fits over the tubulation, and a means tofill the tube and chamber with gas at a low rate of inflow toatmospheric pressure.

3 Claims, 3 Drawing Figures PATENTEDJHLZS m2 SCRIBE CIRCUMFERENTIAL CUTON TUBULATION POSITION TUBULATION v IN CLOSE FITTING CLOSED CHAMBERlNVEN'TOR. Earle 8. Thall BY ATTORNEY CRACK TUBULATION ALONG CUT INCLOSED CHAMBER SLOWLY FILL CHAMBER AND TUBE WITH GAS Fig. 3.

METHOD FOR FILLING AN EVACUATED ELECTRON TUBE WITH GAS TO ATMOSPHERICPRESSURE BACKGROUND OF THE INVENTION In one prior method for opening anevacuated cathode-ray tube tube described in U.S. Pat. No. 3,063,777 toA. M. Trax, a portion of the neck is cracked off with a hot wire anddiscarded. Cracking off the neck permits entry of gas at atmosphericpressure. When this method is applied to regunning shadow-mask-typecolor-television-picture tubes, the gas enters so rapidly that glassparticles obtained from cracking the neck may be swept into the tube andmay result in blocked mask apertures.

In a second method for opening an evacuated cathode-ray tube describedin U.S. Pat. No. 3,404,933 to R. J. Weideman, a portion of the tube andthe tipoff tabulation are positioned in a chamber. The chamber isevacuated, after which the tabulation is broken by impact from a pointedend of a plunger. A dry inert noncontaminating gas is then admitted intothe evacuated envelope. This second prior method requires evacuationequipment since a substantially large chamber must be evacuated. Onlyafter the chamber is evacuated may the exhaust tubulation be broken inorder to prevent particles from being swept into the opened tube by theinrush of gas at atmospheric pressure. In addition, when the tubulation.is broken by impact from a plunger, many small glass particles aregenerated, some of which may enter the tube as a result of the impactforce of the plunger and be further swept into the tube during gasfilling of the tube. These particles may contaminate the tube, which mayresult in defective performance of the tube after reevacuation.

SUMMARY OF THE INVENTION The novel method includes scribing or otherwisemaking a circumferential cut on the glass exhaust tubulation of anelectron tube, positioning the tubulation inside a close-fitting, closedchamber, cracking the tubulation on the cut, and slowly filling the tubewith gas at a low rate of inflow to atmospheric pressure.

Unlike the prior methods, the exhaust tubulation of the tube is placedin a small close-fitting, closed chamber containing a small internal gasvolume. By enclosing the tubulation in a close-fitting, closed chamberhaving a minimum volume, no substantial inrush of gas occurs uponopening the tube in the chamber, and there is no requirement to evacuatethe chamber to prevent an initial inrush ofgas.

In addition, the novel process provides for opening the tube by crackingthe tubulation on a previously prepared cut. By cracking the tubulationon the cut, a minimal quantity of glass particles is formed, By crackingthe tubulation inside the close-fitting chamber, particles are not sweptinside the tube from the initial inrush of gas, thereby avoidingblocking of the mask apertures and particle contamination. This novelprocess permits cost reduction in opening of evacuated tubes for repairby obviating the need for evacuation equipment, an evacuated chamber, ora gas filled chamber, resulting in more economical rebuilding ofelectron tubes.

The novel apparatus includes a means for cracking the tubulationcomprising a closed chamber having a flexible portion and a solidportion. The flexible portion seals over the tubulation, and the solidportion fits over the tubulation substantially conforming and closelyspaced from the tubulation. The apparatus includes a means to fill thetube chamber at a substantially low rate of inflow to atmospheric airpressure. The novel apparatus is of a simple structure, which iseconomical to operate and maintain.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional elevational viewof a scribing assembly used in practicing the novel method.

FIG. 2 is an elevational view, partially in broken sections, of atubefilling assembly used in practicing the novel method.

FIG. 3 is a flow diagram showing the steps of the novel method.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 and FIG. 2 include thebottom portion of an electron tube 10 (partially shown) having a glassenvelope 1] including a neck 12, stem leads 13, and glass exhausttubulation 14 with tipoff 15 positioned in apparatus for opening thetube 10 to air at atmospheric pressure.

The apparatus shown in FIG. 1 is a tubulation-scribing assembly 16. Thescribing assembly 16 includes a handle 17 having a handle hole 18 in oneend slightly larger than the maximum diameter of the tubulation 14. Acutting tool 19 having a cutting point 20 extends through the handle 17in a radial hole 21. The scribing assembly 16 includes a means forradially moving the cutting tool 19 in the radial hole 21 comprising aspring 22 attached between the cutting tool 19 and the handle 17 and acollar 23 mounted over the handle 17 having a spring adjustment 24 incontact with the spring 22. The col lar 23 also slides axially on thehandle 17 to act as an adjustable stop when against the stem leads 13.

Referring to FIG. 2, a tube-filling assembly 25 includes a small,close-fitting hermetic chamber 26 formed by a flexible tubular portion27 and a cylindrical rigid portion 28. The flexible portion 27 has aslightly smaller inner diameter than the outer diameter of thetubulation 14. One end of the flexible portion 27 is stretched to fitover the tubulation 27, and the other end is stretched to fit over therigid portion 28. The rigid portion 28 has an axial hole 29 in one endof slightly larger diameter than the maximum diameter of the tubulation14.

In the preferred embodiment, the diameter of the tubulation 14 is in therange of 0.349 0.365 inch, the inner diameter of the flexible portion 27is approximately one-fourth inch, the wall thickness of the flexibleportion 27 is approximately onesixteenth inch, and the diameter of theaxial hole 29 is approximately three-eighths inch. The flexible portion27 may be a rubber or plastic tubing. The preferred tubing is marketedby U.S. Stoneware Inc., Akron, Ohion, under the trade name tygon"flexible plastic tubing. A needle valve 30 having a flowcontrol knob 31is attached to the other end of the rigid portion 28. An axial passage32 connects the axial hole 29 and the needle valve 30. An air filter 33is connected onthe other end of the needle valve 30.

In the operation of the apparatus, the steps of the novel method areshown in FIG. 3. The tubulation-scribing assembly 16 shown in FIG. 1 ispositioned with the handle hole 18 over the tubulation 14, the collar 23in contact with the end of the stem leads l3, and the cutting pointagainst the side of the tubulation 14. The spring adjustment 24 is thenrotated to apply pressure on the spring 22 to maintain the cutting point20 in contact with the side of the tubulation 14. The scribing assemblyI6 is then rotated, making a circumferential cut 34 on the outer surfaceof the tubulation 14. It is preferred that the circumferential cut 34 beabout half way the length of the tubulation 14.

After the circumferential cut 34 is made, the scribing assembly 16 isremoved from the tubulation l4, and the filling assembly 25 is placedover the tubulation 14, as shown in FIG. 2, with the tubulation 14positioned in the chamber 26. In this position, the axial hole 29 in therigid portion 28 fits over the tubulation l4 enclosing the tubulation 14between the cut 34 and the tipoff 15. The flexible portion 27 fits overthe tubulation 14, between the cut 34 and the neck 12, sealing againstthe tubulation 14, making the chamber 26 airtight. The open end of theflexible portion 27 also contacts the end of the neck 12 to position theend of the rigid portion 28 approximately aligned with or slightly belowthe cut 34.

With the tubulation 14 in the chamber 26 and the needle valve 30 closed,the tubulation 14 is cracked at the cut 34 by supporting the tube andapplying a traverse pressure on the tube-filling assembly as shown bythe direction arrow 35. This traverse pressure moves the fillingassembly 25 to the position 36 (shown in phantom), which cracks thetubulation l4 completely through at the cut 34.

Since the tube is opened only to a small, close-fitting her meticchamber, substantially no inrush of air occurs. In addition, by crackingon the previously prepared cut 34, a minimum number of particles arecreated. The needle valve is then opened by rotating the knob 31 toslowly admit air into the chamber 26 and tube, subsequently filling thetube 10 with air to atmospheric pressure. The needle valve 30 isadjusted to slowly bleed air into the tube 10 and chamber 26 at a lowinflow rate to atmospheric pressure. It is preferred that the inflow fora 25-inch color-picture tube fill the tube with air in 30 minutesminimum, and preferably longer to prevent particles from being sweptinside the tube 10.

I claim:

1. A method for opening to a gas at atmospheric pressure an evacuatedelectron tube including an envelope having a glass exhaust tubulationwith tipoff projecting therefrom comprising the steps of:

it making a circumferential cut on said tubulation, said cut aboutmidway the length of said tubulation,

2. positioning said tubulation with said cut portion contained within aclose-fitting, closed hermetic chamber,

3. cracking said tubulation along said out in said closed chamber,

4. and slowly filling said chamber and tube with said gas at a lowinflow rate.

2. The method defined in claim 1 wherein said chamber includes aflexible portion and a rigid portion, said flexible portion sealing withsaid tubulation between said cut and said glass envelope, and said rigidportion enclosing and substantially conforming to and spaced from saidtabulation between said out and said tipofi", and said cracking stepcomprises applying a traverse pressure on said rigid portion, saidflexible portion distorting to remain sealed with said tubulation.

3. The method of claim 1 wherein said inflow rate fills said tube toatmospheric pressure in 30 minutes minimum time.

1. A method for opening to a gas at atmospheric pressure an evacuatedelectron tube including an envelope having a glass exhaust tubulationwith tipoff projecting therefrom comprising the steps of:
 1. making acircumferential cut on said tubulation, said cut about midway the lengthof said tubulation,
 2. positioning said tubulation with said cut portioncontained within a close-fitting, closed hermetic chamber,
 3. crackingsaid tubulation along said cut in said closed chamber,
 4. and slowlyfilling said chamber and tube with said gas at a low inflow rate. 2.positioning said tubulation with said cut portion contained within aclose-fitting, closed hermetic chamber,
 2. The method defined in claim 1wherein said chamber includes a flexible portion and a rigid portion,said flexible portion sealing with said tubulation between said cut andsaid glass envelope, and said rigid portion enclosing and substantiallyconforming to and spaced from said tabulation between said cut and saidtipoff, and said cracking step comprises applying a traverse pressure onsaid rigid portion, said flexible portion distorting to remain sealedwith said tubulation.
 3. The method of claim 1 wherein said inflow ratefills said tube to atmospheric pressure in 30 minutes minimum time. 3.cracking said tubulation along said cut in said closed chamber,
 4. andslowly filling said chamber and tube with said gas at a low inflow rate.